Industrial paint spray installations often incorporate a system for effecting a color change cycle. Such systems are desirable in high volume production operations where several differently colored products are produced in a typical production day. The prior art has heretofore offered several advantageous arrangements for effecting a color change. Representative of prior proposals are the systems of the Richard F. Wiggins U.S. Pat. No. 3,348,774 and the Richard F. Wiggins co-pending application Ser. No. 468,973, filed May 10, 1974, both owned by The Gyromat Corporation. The subject matter of Wiggins copending application Ser. No. 468,973, filed May 10, 1974 is hereby incorporated by reference into the present application.
In accordance with the teachings of both of these prior proposals, a discharge or purge system is connected to the paint delivery system for each of the several spray devices, substantially at the spray devices themselves, as close to the spray discharge outlet as is reasonably practicable. For example, in the improved system of the co-pending application, a purge line header is connected to each spray device through an individual check valve and an individual purge line connected at a point downstream of the spray device's fluid regulator. The purge header line is connected through a first trap valve, an elongated inventory line and a second trap valve to a purge outlet line.
While the above-described system is ideally suited for typical industrial paint spray installations, efficient operation of the system requires reliable functioning of the individual check valves in a difficult environment. A sticky check valve or plugged duct valve, can, for example, result in an occasional failure to properly discharge and segregate different colors of purged paints, with consequent loss of paint recovery efficiency.
Accordingly, it is the basic objective of the present invention to provide a novel and improved, positive check valve control unit to insure the proper functioning of all check valves in a color change system or the like. Generally, the new positive check valve control unit comprises a valve body provided with a common outlet duct and a plurality of individual check valves attached thereto. In practical applications the valve body will be provided in a square or hex stock, for example, to accommodate four or six check valves (one to a side).
Each check valve will include a passage with a discharge opening for communication with the common outlet duct. The valve action comprises a ball check movably positioned in the passage and biased by biasing means against the common outlet duct opening with the ball check protruding into the common duct. In one advantageous form, spring means can be used to bias the ball check. In other forms, the biasing can be achieved by a magnet and steel ball arrangement or by pressure developed by fluids in the color change system, for example.
To particular advantage, the present invention provides a unique cam plunger arrangement in the common outlet duct, for displacing the protruding ball checks outward against the biasing means, to positively open the check valves. The plunger is actuated in conjunction with the color change cycle to insure that the check valves open properly when required. The cam is attached to the end of a plunger shaft which lies along the center axis of the common outlet duct and extends through a bore in the valve body to engage an actuator disc of an actuating means enclosed within the valve body. To advantage, an air activated bellows assembly can be utilized as the actuating means.
Normally, spring means acting between the valve body and actuator disc axially retracts the plunger shaft and attached cam plunger out of contact with the ball checks so that the check valves remain in a closed position. When it is desired to open the check valves the bellows is expanded by the introduction of air under pressure causing the actuator disc to move against the spring means and impart axial movement to the plunger shaft and cam. This advances the cam plunger to its ball check displacing position. Conveniently, the bellows can be actuated with high pressure air from an air-paint override solenoid already employed as an element in the above described color change systems. In other forms of the invention, an electrical relay or similar device can be employed as the actuating means.
For a better understanding of the above and other features and advantages of the invention, reference should be made to the following detailed descriptions, and to the accompanying drawings.